The present invention relates to a process for the preparation of the surface of uranium parts or uranium-based alloy parts, carried out with a view to obtaining on said parts nickel coatings by using a chemical nickel-plating process.
In several fields, it is often necessary to deposit nickel coatings on uranium or uranium alloy parts. Generally these coatings are produced by electrolytic nickel-plating, which makes it possible to obtain coatings with a satisfactory quality. However, these electrolytic nickel-plating processes are not suitable for the treatment of parts having a complicate shape, e.g. with reentrant angles and/or holes because, in this case, it is difficult to obtain a uniform nickel deposit thickness and sometimes it is even difficult to entirely coat the surface of the parts. In addition, in the case of parts having a complicated shape, it is preferable to carry out nickel deposition chemically, in order to overcome these difficulties.
However, in order to obtain a nickel coating having an adequate adhesion by chemical nickel-plating, it is firstly necessary to subject the part to a preparatory surface treatment which can e.g. be carried out by chemical etching and which must lead to a uniform and thickness-controllable etching, so that the surface of the part is able to receive the nickel deposit.
Several surface treatments of this type are described in French Pat. No. 1 564 575 filed by the C.E.A. These treatments can in particular comprise trichloroethylene cleaning, cathodic electrolytic cleaning and pickling using nitric and hydrochloric acids. It is also possible to replace the hydrochloric acid by a solution of copper chloride and hydrochloric acid, or carry out a complementary electrolytic pickling stage in a sodium acetate solution.
Such treatments lead to a satisfactory result, except in the case of parts having a complicated shape, where it is difficult to obtain a homogeneous, thickness-uniform etching over the entire surface of the part.
The present invention specifically relates to a process for the preparation of the surface of a uranium or uranium alloy part making it possible to obtain a good surface state over the complete part.